Want a quick and inexpensive call for Moose? Take an empty 32 ounce coffee can, and make a small slit in the bottom, only about a quarter inch. Then, take one of those really big red rubber bands, the ones that go around big folders. Cut the rubber band to make one long piece.
Now, thread one end of the band and tie a knot on the outside of the can so it won't pull through. Cut the band off on the other side so it is even with the top of the can.
Now, wet your finger, reach in, and squeezing slightly on the band, pull on it. Don't over wet your fingers. There should be a little friction there to create the groaning noise as it slips through your finger. The can will echo the sound perfectly.
I watched my grandfather do this and get responses from multiple bulls up in Maine. Even just for fun one evening if you live in moose country, give it a try!!!